Hematite Curie temperature

Fig. 6.7 Temperature dependence of the magnetic properties of hematite. Tc = Curie temperature,Tm = Morin temperature, pm = paramagnetic region, wfm = weakly ferromagnetic region afm = antiferromagnetic region. The insets show simulated Mossbauer spectra of hematite in the paramagnetic, weakly ferromagnetic and antiferromagnetic states (Murad, 1988, with permission).

Maghemite is ferrimagnetic at room temperature. Measurement of Tc is difficult because maghemite transforms to hematite at temperatures above ca. 7-800 K. The Curie temperature has been estimated as lying between 820 K and 986 K (Murad, 1988). 

Fig. 6.9 Left Relationship between the Curie (Tc) and Morin (Tm) temperature of hematite and the extent of structural substitution of Fe " by Al, Ga, Cr and In (M) (Svab Kren, 1979, with permission). Right Relationship between the Morin temperature and the inverse mean crystal dimension (MCD) for different hematites ( ) natural from Elba ( ) heating lepido-...

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